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12. Subwoofer setup procedure
Figure: Sample measurement of an LT 7 frequency response
The sample measurement shown above illustrates
how severely a room's acoustic properties can af-
fect the linear frequency response curve of the
M 7200 SW.
Step 9: Now, let's use the M 7200 SW's versatile
setup options to flatten out this frequency curve.
There are a few things to watch out for:
Generally, you should only use the paramet-
4
ric equalizer for reducing excessive peaks in
the response curve, e.g., the peak at 60 Hz
in the sample chart. If you need to use the
parametric equalizer to boost a section of the
frequency range, make sure not to boost more
than a few dB.
Dips in the frequency curve (such as the
4
30 Hz dip in the sample chart) usually result
from phase cancellations, which are caused
by the same frequencies being produced by
different speakers at different polarities. You
cannot fix phase cancellations through equali-
zation; the best remedy is to reposition the
subwoofer.
Many of the minor dips and boosts in the
4
frequency range are directly caused by the
acoustic properties of the room, and these
cannot be fully eliminated unless the physical
room acoustics are painstakingly matched to
the speaker setup. In practice, it usually isn't
feasible to attain a fully linear frequency re-
sponse, so the sensible approach is to find the
best-sounding compromise.
Frequency peaks are generally more discern-
4
ible and detracting than frequency dips. There-
fore, our aim should always be to eliminate the
peaks in the frequency curve rather than com-
pensating for the dips.
We recommend that you fine-tune the sub-
4
woofer's physical position and sound controls
so that any extreme dips are shifted into that
part of the frequency range where there is the
least signal content (i.e., at the bottom end of
the sub-bass region or well above the subwoof-
er's crossover frequency). While this doesn't
fix the problem of resonant frequencies in the
room, it does effectively minimise their inter-
ference.
In spite of all the acoustic theory, the final
4
judge should always be your subjective listen-
ing experience. It isn't at all unusual to opt
for a non-linear frequency response curve if it
pleases your ears – for example, you may enjoy
a boost in the sub-bass frequencies.
After you have modified the subwoofer's set-
4
tings and/or physical position, run a new fre-
quency measurement to record the updated
frequency response curve.
Teufel · LT 7
33
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